With what I've read in this thread, I have two of the 'thinner' blocks as they measure 5mm at the screw holes. They're both still in the box, unmounted - I supposed I should wait to hear back from Eddy before going further? I have the aluminum back plates and also ordered the WC back plates to go with my 2 280's in a Striker II Extreme board... I have some time to get this all resolved but I want to make sure and get it right the first time.

You have a PM and email Eddy. It's greatly appreciated how forthright you've been regarding this issue.